Modern enterprise communication systems often combine call processing and Internet Protocol (IP) telephony capabilities with a private branch exchange (PBX) system in a way that extends enterprise telephony features and functions to packet telephony network devices such as IP phones, media processing devices, voice-over-IP (VoIP) gateways, and multimedia applications. Typical features of such systems include unified messaging and multimedia conferencing capabilities. Additionally, the pervasive growth in voice and data networks has lead to the development of ever more sophisticated communication and messaging systems that enable users to send and retrieve voice, text, and electronic mail messages from a variety of communication devices.
A unified messaging system (UMS), such as the commercially-available Cisco® Unity integrated system, handles voice, facsimile and regular text messages as objects in a single mailbox that a user can access either with a regular email client, or by telephone. A UMS typically connects to an IP-PBX to provide automated attendant, audiotext, and voice mail services to subscribers or users. For instance, a personal computer (PC) user with multimedia capabilities can open and playback voice messages, either as speech or text. Similarly, a person may retrieve their email messages as speech from a voice-over-IP (VoIP) phone connected through an IP network, or from a traditional telephone device connected with the enterprise via a conventional public switched telephone network (PSTN). Unified messaging is thus particularly convenient for mobile business users because it allows them to reach colleagues and customers through a PC or telephone device, whichever happens to be available.
An example of a unified messaging system is found in U.S. Patent Publication No. 2005/0177622, which teaches a scalable UMS that outputs a notification delivery message according to a prescribed open protocol based, in part, on a subscriber's notification preference. U.S. Patent Publication No. 2005/0157708 teaches a system and method providing UMS services that includes a PSTN interface for a telephone network service, a VMS, a facsimile, and an IP interface for connection to a packet-based network for an Internet messaging (e.g., an email service).
As networks have grown larger and use of electronic communication devices has become ubiquitous, the risk of improper interception of data and messages containing confidential information has risen. To combat the problem of unwarranted interception or eavesdropping of confidential information, sophisticated data encryption algorithms have been utilized to encrypt data and email messages prior to transmission, thereby securing the communication channel. By way of example, U.S. Pat. No. 6,905,414 teaches a secure communication mechanism for communicating credit card or other sensitive information transmitted over a data network (e.g., Internet). Similarly, a method for enabling secure communications over a network that employs a public/private key encryption algorithm through a secure communication device is described in U.S. Patent Publication No. 2003/0061496.
In many enterprises, mail encryption schemes are commonly employed to protect confidential email messages transmitted outside of the enterprise. However, if the email recipient's messaging system is a unified messaging system, then a user may listen to his email messages over an unsecured telephone line or voice channel. For instance, a recipient may listen to an email message using his cellular telephone (i.e., cellphone) over an unsecured voice channel of a wireless cellular network service provider, thereby defeating the entire encryption scheme that was originally intended to protect the message content.
Therefore, what is needed is a system and method of operation that ensures that sensitive or confidential voicemail or email messages cannot be retrieved or heard over an unsecured or unencrypted voice channel.